What is the principal behind Ostwald Isolation Method to find the order of a reaction ?

The principle behind this method is that if the concentration of all but one reactant is taken in excess, then during the course of reaction, the concentration of those reactants taken in excess will remain constant and the variation in the rate will correspond to the concentration of that reactant whose concentration is small. The process is repeated for other reactants present in the chemical reaction one by one and order with respect to each reactant can be determined.What is the principal behind Ostwald Isolation Method to find the order of a reaction ?
This method is used when there are more than 1 reactants.





The basic principle is that when one reactant is taken in large excess compared to the other reactant, the change in concentration in the first reactant is negligible.


Consider the reaction:


A+B--------%26gt;products


First, A is taken in small amounts while B in large excess. This way, the change in concentration of B is negligible and can be taken as a constant. Now the order of the reaction with respect to A is determined by a suitable method. Let's say it's x.





Next, B is taken in small amounts and A in large excess. The order of the reaction with respect to B is determined. Let's say it is y.





The overall order of the reaction is given by x+y.








Hope this is clear.